Production of unsaturateb



Aug. 12, 1952 R. M. COLE EI'AL PRODUCTION OF UNSATURATED CARBONYLIC COMPOUNDS 2 srmE'rs-si-mm 1 Filed July :51, 1950 ZEJOMUdzPMS MP OP 3 mm 5" X 5 uumuowm ROBERT M. coua CLARENCE L. DUNN 55:40 J. PIEROTTl BY THUR AGENT M INVENTQRS Aug. 12, 1952 R. M. COLE ETAL 2,506,933

PRODUCTION OF UNSATURATED CARBONYLIC COMPOUNDS Filed July 31, 1950 2 SHEETS-SHEET 2 PHASE. szmzxrouz '0' FIGJHQ QUENCH TOWER mvemoas: ROBERT M. COLE.

CLARENCE L. DUNN (21 J. MEROTTI BY mam AGENT latented Aug. 12, 1952 PRODUCTION OF UNSATURATEB CARBONYLIC COMPOUNDS Robert M. Cole, Oakland, Clarence L; Dun'ii, Berkeley, and Gino J. Pierotti, Albany, Califi, assignors to Shell Development Company,- San Francisco, Calif., a corporation of Delaware Application July 31, 1950, Serial No. 176,854

7 Claims. 1

This invention relates to the production of alpha,beta-unsaturated carbonylic compounds by the oxidation of hydrocarbons having at least three carbon atoms to the molecule. The invention relates more particularly to the production of alpha-methylene aldehydes and ketones by the oxidation of olefins having at least three carbon atoms to the molecule. A particular aspect of the invention relates to the production of alphamethylene aldehydes having from three to four carbon atoms to the molecule by the oxidation of normally gaseous hydrocarbons comprising the corresponding olefins.

Production of alpha,beta-unsaturated carbonylic compounds on a practical scale generally results in the obtaining of a crude product comprising a desired unsaturated carbonylic compound in admixture with substantial amounts of by-products unavoidably formed during the process. The ability to utilize the unsaturated carbonylic compounds, such as the alpha-methyh ene aldehydes and/or ketones efficiently in many fields of application is often dependent upon the absence therein of any substantial amount of impurities. The large-scale production of an alpha,beta-unsaturated aldehyde or ketone of relatively high purity is of necessity, limited to methods enabling the obtaining of a product comprising the unsaturated carbonylic compound in admixture with impurities which are readily separable therefrom by available practical scale separating means. Thus, the production of acrolein from such starting materials, as for example, acetaldehyde and formaldehyde under carefully controlled conditions often enables the attainment of a product comprising the acrolein in ad mixture with impurities consisting essentially of acetaldehyde, formaldehyde and relatively highboiling organic materials. All of such impurities are readily separable from the acrolein on a practical scale by methods available heretofore comprising such steps as simple fractionation, water Scrubbing, distillation, and the like. Although acrolein of relatively high purity can be obtained by such methods these processes are generally handicapped by unavailability at sufficiently low cost of the starting materials. A particularly valuable source of the unsaturated carbonylic compounds comprises the products obtained by the oxidation of the readily available hydrocarbons. It has been found recently that the readily available hydro-carbons comprising olefins having at least three carbon atoms to the molecule, can be converted efiiciently to products consisting predominantly of alpha,betaunsaturated carbonylic compounds, such as, for example, the alpha,beta-unsaturated aliphatic aldehydes and ketones by catalytic oxidation. Thus,

unsaturated carbonylic compounds consisting essentially .of acrolein and 'methacrolein are obtained by the catalytic oxidation of propylene and isobutylene, respectively. The efliuence from the hydrocarbon oxidizing zone in such processes, however, is an exceedingly complex mixture and contains the desired unsaturated carbonylic compound in admixture with saturated carbonylic compounds such as saturated aldehydes and ketones inseparable therefrom on a practical scale by the methods applicable to the treatment of less complex mixtures. The production of an alpha,beta-unsaturated aliphatic aldehyde from the corresponding olefin, such as, for example, the production of acrolein from propylene', resuits in the production or a complex mixture com-' prising the acrolein in admixture not only with readily separable impurities such as formaldehyde, acetaloehyde, and high-boiling material but also close-boiling carbonylic compounds such as, for example, propionaloehyde and acetone, inseparable thererrom on a practical scale by simple distillation, Water scrubbing, or the like. lnabile ity to efiect the enicient and yet substantially complete recovery of the unsaturated aldenydes' from the hydrocarbon oxidation products c'on taining them has militated against any full r'ealization of the substantial advantages as a source or" these highly desirable and valuable compounds.

In co-pending applications: Serial Nos. 1,314, now U. S. Patent No. 2,514,966, 49,816, now U. S. Patent No. 2,514,967 and 84,074 there have been described and claimed methods for the recovery of alpha,beta-unsaturated alde hydes from the crude alpha,beta-unsaturated aldehydes comprising saturated carbonylic impurities having boiling temperatures approximating those of the alpha,beta-uns aturated al-' dehydes. These processes, however, generally necessitate the initial separation of a crude alpha,beta-unsaturated aldehyde from the efiluence from the hydrocarbon oxidizing zone. The

separation of a crude unsaturated aldehyde may be effected by scrubbing the hydrocarbon oxidation products emanating from the hydrocarbon oxidation zone with water to effect a substantially complete separation of normally gaseous materials, generally including fixed gases and unconverted hydrocarbons, from carbonylic 'hydrocarbon reaction products. Such separation generally necessitated the use of exceedingly large quantities of water. The passage of such inordinately large amounts of water through such scrubbing zone not only renders difficult the maintenance of relatively constant conditions conducive to the attainment of optimum results, but materially increases initial installation and overall operating costs of the process. In such method of operation not only all of the inert gas but also substantially all unconverted hydrocarbons are passed overhead from the scrubber. Since operation of the process on a practical scale necessitates the recycling of unconverted hydrocarbons, inordinately large volumes of material must be passed overhead from the scrubber to a suitable recycle recovery system in such processes. Further difficulties inherent in such methods of operation as used heretofore reside in the fact that the maximum permissible pressure within the product scrubber is governed by the pressure at which the hydrocarbon components of the charge thereto begin to condense. The use of water as scrubbing medium generally allows relatively little variation of conditions within the scrubber without incurring either the condensation of excessive amounts of hydrocarbon or the highly undesirable consequence involving the passage of carbonylic constituents overhead.

It is an object of the present invention to provide an improved process enabling the more efficient production of alpha,beta-unsaturated carbonylic compounds by the oxidation of hydrocarbons wherein the above diffioulties are obviated to at least a substantial degree.

Another object of the invention is the provision of an improved process enabling the more eificient production of alpha,beta-unsaturated carbonylic compounds by the oxidation of olefinic hydrocarbons wherein difiiculties heretofore encountered in the separation of carbonylic compounds from the hydrocarbon oxidation zone effluence. are obviated to at least a substantial degree.

A more particular object of the invention is the provision of an improved process enabling the more efiicient production of alpha,beta-unsaturated hydrocarbons having from three to four carbon atoms to the molecule by the oxidation of hydrocarbons comprising olefins having from three to four carbon atoms to the molecule.

A still more particular object of the invention is the provision of an improved process enabling the more efiicient product of methacrolein by the oxidation of normally gaseous hydrocarbons comprising isobutylene. Other objects and advantages of the invention will become apparent from the following detailed description there.

It has been found, as disclosed and claimed in co -pending application Serial No. 176,853, filed July 31, 1950, of which the present application is a continuation-in-part that substantially improved production of alpha,beta-unsaturated carbonylic compounds, by catalytic oxidation of hydrocarbons comprising olefins, is obtained by introducing at least a part of the olefinic hydrocarbon feed to the process into an absorption zone wherein said feed is brought into direct contact with efiiuence from the hydrocarbon oxidation zone under conditions effecting the separation of carbonylic components from said reactor efliuence with the formation of a fraction in the liquid state comprising said carbonylic compounds and said hydrocarbon feed and a gaseous fraction comprising fixed gases. Carbonylic compounds are recovered from the fraction separated in theliquid state in the absorption zone, and hydrocarbon components remaining after such separation are introduced into the hydrocarbon oxidation zone of the process wherein they are subjected to conditions resulting in the oxidation of hydrocarbons to reaction products comprising alpha,beta-unsaturated carbonylic compounds.

Realization to the full of the advantages inherent in the improved process, however, often are handicapped by the formation in the system of carbonylic by-products which are inseparable from, or can be separated only with great difiiculty from, the hydrocarbons to be oxidized by such means as simple distillation, ordinary fractionation, and the like. Contacting the hydrocarbons to be oxidized with oxidation zone effiuence prior to their passage into the oxidation zone will often result in an accumulation of such by-product carbonylic impurities in the system rendering difficult the maintenance of optimum operating conditions and the eihcient obtaining of maximum yields. It has now been found that these further diiiiculties are obviated to at least a substantial degree by subjecting simultaneously both the contaminated hydrocarbons to be oxidized and the crude alpha,betaunsaturated carbonylic product to a common purification step which removes the carbonylic impurity from said contaminated hydrocarbons to be oxidized while simultaneously effecting the purification of the desired alpha,beta-unsaturated carbonylic product. For example, in the production, in accordance with the invention, of an alpha,beta-unsaturated carbonylic compound, such as methacrolein, by the controlled catalytic oxidation of normally gaseous hydrocarbons comprising isobutylene, the normally gaseous hydrocarbons to be oxidized are passed in the liquid state through an absorption zone countercurrent to methacrolein-containing eiiluence from the hydrocarbon oxidation zone, thereby separating methacrolein-containing carbonylic compounds from the effiuence of the hydrocarbon oxidizing zone with the formation of a liquid fraction consistin essentially of hydrocarbons comprising iscbutylene and methacroleincontaining carbonylic compounds and a gaseous fraction comprising fixed gases. The liquid fraction formed in the absorption zone is fractionated to separate therefrom a fraction consisting essentially of normally gaseous hydrocarbons comprising isobutylene unavoidably contaminated by the presence therein of carbonylic impurities and a fraction comprising methacrolein-containing carbonylic compounds. The fraction comprising methacrolein-containing carbonylic compounds is subjected to a liquid phase solvent extraction using water as the selective solvent in the presence of said contaminated normally gaseous hydrocarbon fraction comprising isobutylene as a secondary solvent, thereby forming a raifinate phase consisting essentially of methacrolein and isobutylene substantially free of contaminant carbonylic compounds. Isobutylene, substantially free of carbonylic compounds is distilled from the rafflnate phase, thereby leaving as residue the desired methacrolein in a high state of purity. The isobutylene, substantially free of carbonylic impurities, which is distilled from the raffinate phase of the solvent extraction step, is employed as the normally gaseous hydrocarbon charge to the oxidation zone of the process.

Conditions maintained Within the hydrocarbon oxidation zone of the process comprise broadly those capable of converting hydrocarbons to carbonylic reaction products comprising alpha,beta unsaturated carbonyiic compounds. Particularly preferred conditions to be maintained Within the reaction zone of the process comprise the catalytic hydrocarbon oxidizing conditions set forth in United States Patent 2,451,485 under which conaeeaesa ditions hydrocarbons containing olefins having at least three carbon atoms to the molecule are converted to alpha-methylene carbonylic compounds, that is, to unsaturated aldehydes and ketones containing an olefinic linkage between two carbon atoms of aliphatic character, one of which carbon atoms is directly linked to an aldehyde or ketone group. Under the conditions of said patent the desired hydrocarbon oxidation is obtained by contact of the hydrocarbon charge in admixeture with oxygen, or an oxygen-containing gas, with a cuprous oxide-containing catalyst at a temperature in the range of from about 150 C. to about 600 0., and preferably from about 200 C. to about 450 C. V

Olefins having three or more carbon atoms to the molecule capable of being converted to alphamethylene aldehydes and ketones, also referred to as vinyl-type aldehydes and ketones or alpha,- beta-unsaturated aldehydes and ketones in ac-' cordance with the invention, comprise the openand closed-chain olefins such, as, for example, propylene; butene-l, butene-Z; isobutylene; pentene-l, pentene-2; B-methyl-butene-l; 2-methylbutene-2; hexene-l; 4-methyl-pentene-l; 3,3- dimethyl-butene-l; 4-methyl-pentene-2; octene- 1; cyclopentene; cyclohexene; 3-methylcyclohexene, etc. The hydrocarbons converted to the unsaturated carbonylic compounds within the hydrocarbon oxidizing zone of the process may comprise other hydrocarbons such as, for example, parafiinic hydrocarbon of straight or open-chain structure which may or may not undergo reaction under the oxidation conditions employed within the oxidation zone of the process,

Additional materials such as, for example, normally gaseous materials or normally liquid materials which are vaporized, or which are in the gaseous state under the conditions of execution of the hydrocarbon oxidation reaction may be introduced into the hydrocarbon oxidation zone. In a preferred method of carrying out the process of the invention the hydrocarbon oxidation reaction is executed in the presence of added water. vapor.

The process of the invention is applied with particular advantage to the production of alpha, beta-unsaturated aliphatic aldehydes and ketones having three and four carbon atoms to the molecule by oxidation of normally gaseous hydrocarbons comprising olefins having from three to four carbon atoms to the molecule. In order to setforth more fully the nature of the invention it will be described in detail herein to the production of methacrolein from normally gaseous hydrocarbons comprising isobutylene with refer.- ence to the attached drawings wherein Fig. I represents a more or less diagrammatic elevational view of one form of apparatus suitable for carrying out the process of the invention, and Figs. II and III each represents a diagrammatic elevation view of an alternative form of that portion of apparatus of Fig. I between reactor 15. and absorber 30. Identical parts of the apparatus e. be n in i ates i ifi gftae r wi by likev reference characters. Y

Referring to Fig. I of'the drawing hydrocarbons having at least three carbon atoms to.

the molecule, for example, a stream of-normally gaseous hydrocarbons comprising isobutylene, emanating from withinthe system "as described more fully hereinbelow, are forced through lines H) and H, coil 13 positioned in housing I2, and transfer line 14, into a suitable reaction zone. The reaction zone may comprise "one or more zones of enlarged cross-sectional area,,suchas, for example, a reaction chamber I5. The reac-- tion zone may furthermore comprise one or more zones of restricted cross-sectional area, not shown in the drawing, such as a coil or tubular reactor. Oxygen, or an oxygen-containing gas, such as air, taken from an outside source is forced through line I! and coil [8 into transfer line [4 wherein it mingles with the hydrocarbon stream entering reaction chamber l5.

Within reaction chamber 15 the hydrocarbon stream in admixture with the oxygen, or oxygencontaining gas, is contacted with asuitable oxidation catalyst under hydrocarbon oxidizing conditions resulting in the interaction of isobutylene and oxygen with the formation of reaction products comprising methacrolein. As indicated above, the process of the invention is not limited in its application to the use of only certain specific oxidizing conditions within reactor l5 capable of producing methacrolein. Preferred propylene oxidizing conditions, however, comprise those set forth in U. S. Patent 2,451,485 under which propylene reacts with oxygen with the formation of reaction products comprising acrolein.

Temperature conditions within reactor [5 are maintained by controlling the heat input into the streams flowing through coils l3 and I8, and optionally by other means not shown in the drawing. Steam is preferably introduced intothe reaction zone. Water taken from an outside source by means of a line 20 is, therefore, forced into line I I leading to coil l 3.

Oxidation of theisobutylene-containing hydrocarbons within reactor I5 will result in the obtaining of reaction products comprising not only the desired methacrolein but other reaction products comprising, for example, saturated carbonylic compounds,,such as, acetone; acetaldehyde, isobutyraldehyde, and the like, as well as substantial amount of normally gaseous reaction products such as carbon monoxide, carbon dioxide, nitrogen, etc. In addition, the reaction products will be admixed with considerable quan-,

tities of unconverted hydrocarbons and some water. In the oxidation of isobutylene at a temperature of about 360 C. in the presence of a cuprous oxide catalyst wherein the mole ratio of air to isobutylene charged to the reactionzone is approximately 5, the reactor eiiluence contains approximately 46.2 moles of normally gaseous material consisting predominantly of isobutylene,

nitrogen, carbon dioxide, carbon monoxide, andoxygen, for each mole of total carbonyl compounds. The total carbonyl compounds in the mixture is found to have the following approximate composition:

Per cent by weight Methacrolein 91.6 Acetaldehyde 2.2 Propionaldehyde 1.4 Acetone 3.4 Acrolein -1.4

Practical scale operation of the process necessitates not only the efficient separation of the debated liquid state comprising not only the carbonylic reaction products but also the unconverted normally gaseous hydrocarbons, from a gaseous fraction comprising inert gaseous components of the eilluent stream from reactor ii. In accordance with the process of the invention the efiiuent stream from reactor is passed through line 23 and cooler- 24 into separator 25. Within separator 25, a liquid phase, consisting essentially of 8 umns may be employedwithin the steps of the invention and the hydrocarbon feed to the process apportioned to each of the absorber columns. The invention is furthermore not limited to the use of a column-type absorber and any suitable type of contacting device may be comprised in the absorption zone enabling efficient contact of the hydrocarbon charge and the efiluent stream from reactor 15.

water, condensed by the lowering of the tem- 19 The temperature at which the absorption is perature of' the stream occasioned by passage carried out Within absorber 38 may vary conthrough cooler 24, is separated. The aqueous siderably within the scope of the invention in phase thus formed in separator 25 will comprise accordance with the nature of the components formaldehyde and any higher boiling polymeric comprised in the reactor eifiuence, and of the hymaterial formedin-reactor-IE. 15 drocarbon feed to the system, and the pressure The reactor efliuence; now free of most of its employed. Care is taken to maintain the temwater content, may be passed directly from-sepaperature within absorber 30 below that at which rator'25, through valved lines 32, 2'1, and 28-, into any substantial vaporization of the olefinic hyan absorption zone, such as, for example, an abdrocarbon components ofthe streams charged sorber column 30. In a preferred method of thereto will take place. Thus, in the production carrying out the invention, however, cooling of of methacrolein from normally gaseous hydrothe reactor efiluence, and separation of water carbons comprising isobutylene the absorption therefrom is effected by passage through a plu may be carried out at pressures within the range rality of separate and successive coolers and of from about 100 to about 300 pounds within the separators. Thus, the stream leaving separator 5 absorber 30. Temperature conditions within abthrough line 32 is preferably passed through sorption column 35) are maintained with the aid line 32 and cooler 33 into a second separator 35. of coolers 24, 33 and 38, and optionally by other Reactor eiiiuence now substantially free of water temperature controlling means not shown in the is passed from separator 35, through valved line drawing. 28, provided with compressor 29,into absorber 3'81 The following example is illustrative of the In efi'ecting the cooling, and water separation, in advantages inherent in the method of separating a plurality of steps, substantially all of the water carbonylic compounds from the oxidation zone content is removed from the reactor efiluence efiluent stream by absorption in normally gaseous with the inclusion of not more than exceedingly hydrocarbon charge to the process. small amounts: of methacrolein in the aqueous 35 phase formed in the separators. EXAMPLE -I Within absorber the reactor emuence is In two separate operations isobutylene is oxipassed upward countercurrent to Stream of dized to methacro1ein-containing reaction prodcool liquefied normally gaseous hydrocarbons ucts by contacting'a mixture or" isobutylene and comprising isobutylene, which normally gaseous oxygen, containing a mole ratio of isobutylene to hydrocarbons may constitute at least asubst an- Oxygen of 5 with a cupmus Oxide Catalyst at a tial part-of the entire hydrocarbon charge to the temperature of about The resulting y h normally gasec'lls hydmwl'bcns action mixture is cooled and compressed to the compnsmg lsohutylene' emanating from an u pressure at which a liquid isobutylene phase beside source, are forced through line 31 provided gins to appear The residual gaseous phase f with cooling means- 'a cooler mm the the compressed reaction mixture is introduced upper part of absorber. The hydmcarbons into an absorber column wherein it is contacted emanating from cooler 33 are at a temperature countercurrently with a streamof liquefied isosufiiciently low to assure the introduction of at buwlena Themte of introduction of the m least the greater part of the normally gaseous-hy-- fled isobutylene t t upper t of t dmcarbon Stream mm the upper part of absorber sorber is controlled to result in the obtaining of 3 ill-the liquid State- 00116111910115 Within a methacrolein absorption of 99.9%. Each' of the' sorber 3a are controlled to obtain the absorption, t operations igrepeated d r substantially y the q normally Ou hy rocarbon identical conditions with the exception that str am i t du d th u line 31, of Substan- 5 Water-is substituted for the liquefied isobutylene tially all of the carbonylic compounds contained stream introduced into the upper part of the in the stream entering absorber 36 through line absorber; The absorption is carried outin the 2-8, and preferably also the condensation of at columnhaving the equivalent of ten theoretical least a substantial part of unconverted olefinic plates; Temperature and pressure of the abydrocarbons. sorption and amount of solvent required to ob- Although but a single absorber column is tain the desired degree of' separation are indishown in the drawing it is to he understood that cated inthe following table for each of the a-plurality of twoor more such absorption colseparateoperations.

Table. I

Feed to Absorber (Moles) Moles Sol Temp QC 555: Absorption i ggfi i e 5??? eg s.-

" t- Solvent men s cm em in 53ft? tit; 1533 Mole) sggg 70. i Iscbutylene. O. 743 24. 0 45. 8 8. 11 i0. 9 95.5 --do 0.79s 24cc 46.0 7.52 9. 42 i 0.743 24.0 458 205 276 0.793 24:0 46:0 241 312 Enriched absorbing medium (absorbate) consisting essentially of normally gaseous hydrocarbons comprising isobutylene in admixture with methacrclein-containing carbonylic reaction products are passed from the lower part of absorber 35, through valved lines 39 and 40, into a suitable distillation zone comprising, for example, a fractionating column 4|. Within column 4| the enriched absorbent (absorbate) emanating from column 30 is fractionated to separate a gaseous fraction comprising normally gaseous hydrocarbons comprising isobutylene from a liquid fraction comprising methacrolein-contain ing carbonylic reaction products. The carbonylic compounds produced in reactor I5, as shown above, will comprise saturated carbonylic impurities inseparable from the isobutylene by ordinary fractionating means. Thus, the unsaturated carbonylic by-products, unavoidably produced in the oxidation of isobutylene to methacrolein will include acetaldehyde. Acetaldehyde cannot be removed from isobutylene by ordinary fractionating means due to the existence of an azeotrope between the two compounds. At a pressure of 28 pounds .per square inch absolute the azeotropic mixture of isobutyleneand acetaldehyde is found to contain 7.0% acetaldehyde. The normally gaseous hydrocarbons comprising isobutylene separated within iractionator M as a gaseous fraction will therefore be contaminated by the presence therein of saturated carbonylic impurities comprising acetaldehyde. In continuous operation the direct passage of such a contaminated stream to the oxidation zone of the process would result in the accumulation of the impurity within the system to a degree seriously militating againstthe obtaining of the optimum operating conditions. The liquid fraction comprising methacrolein-containing. carbonylic compounds separated in fractionator 4! will comprise methacrolein in admixture with saturated carbonyliccompounds such as acetone isobutyraldehyde, acetaldehyde, propionaldehyde, etc., from which the methacrolein generally must be separated in a high state of purity. Simultaneous recovery of methacrolein in a high state of purity from the methacrolein-containing carbonylic reaction products, and removal of acetaldehyde impurity .from the normally gaseous hydrocarbons comprising isobutylene is accomplished by passing the liquid fraction comprising methacrolein-containing carbonylic compounds from fractionator 4! through valved lines 44 and 33 into a solvent treating zone-comprising, for example, extraction column 45. Within column 45 the methacrolein-containing carbonylic compounds are subjected. to a liquidliquid solvent extraction using water as a solvent in the presence of a secondary organic solvent. To this efiect, water is introduced into the upper part of column 45 by means of valved line 4! provided with suitable cooling means such as a cooler 48. The vapor fraction consisting essentially of normally gaseous hydrocarbons comprising isobutylene contaminated with acetaldehyde which is separated in fractionator 41, is passed from fractionator 4!, through valved lines 5|, 52 and 53, and through cooler 54, into extraction column 45 as the secondary organic solvent used therein. In pa sing through cooler 54 the hydrocarbon stream is cooled to a temperature sufficiently low to assure that .at least the greater part of the normally gaseous hydrocarbon stream comprising isobutylene is introduced into column 45 in the liquid phase.

.10 The normally gaseous hydrocarbon stream is introduced into column 45 at a point below the introduction of the methacrolein-containing. carbonyliccompounds into the extraction column. The specific temperature conditions maintained within the extractor column 45 may vary within the'scope of the invention depending to some extent upon the particular composition of the materials charged. thereto. Inthe purification of a methacrolein-containing"carbonylic product obtained by the oxidationrof isobutylene in the presence of a cuprous oxide catalyst-and usingacetaldehyde-contaminated normally: gase; ous hydrocarbons comprising isobutylene asthe secondary solvent; temperatures below about 30 C., for example, in the range of from about 0 C. to -about C. have been, foundjsuitable.

The'invention is, however, in no wise limited to the use of only these specific conditions' within column 45 and the conditions set forth broadly in co-pending application Serial 'No. 84,074, filed March 29, 1949, which is directed to the purification of olefin-oxidation products, may suitably be applied. I It is to be pointed out that the proportion of isobutylene-containin'ghydrocarbons separated from methacrolein-containing carbonylic com: pound in fractionator' i l' may vary within the scope of the invention. In general, general con'- ditions are controlled to passsuificient isobutylene-containing I hydrocarbons overhead therein to provide the amount required to junction as part or all of the secondary organic solvent stream introduced into the lower part of column 45. A valvedline 55 is provided to enable; the passage of additional amounts of isobutylene into line'53 should this be required If desired, at least a part of the liquid fraction taken from column 30 through line 39 may be caused to by-pass fractionator 4i and beintroduce f p rectly, into. the, solvent extraction column '45; by judicious manipulation of valves 56. and :5]; in lines 39 and 40,' respectively.

Under the above conditions a raffinate phase will be formed in the upper partof column 45 consisting essentially of Y methacrolein and normally gaseous hydrocarbonscomprising isobutyl ene which is substantially freeof saturated cars bonylic impurities- $1 011 as acetaldehyde The ra'fiinatewphase formfid in column 45ispassed through line 60 into a stripping column 61. In column 5 [the raffinate phase is fractionated tQSGIlarate a vapor fraction consisting essentially of normally gaseous hydrocarbons comprising iso: butylene substantially free of saturated carbonylic compounds, such as acetaldehyde, from aliquid fraction consisting essentially of metha: crolein in a high state of purity. H The liquid fraction consisting essentially of high purity methacrolein is taken from column 6| through valved line 63 as a final product. v

The vapor fractionconsisting essentially of normally gaseous hvdrocarbons comprising is,o-. butylene substantially free of carbonylic. com: pounds, is passed from fractionator .Bl through valved line l0 into line. I I. It is thus-seen that the hydrocarbon charge to reactor l5 comprises the normally gaseous hydrocarbons comprising isobutylene which have functioned not only as the absorbing agent for the carbonylic products in absorber 30 but-also as the secondary organic solvent used in the solvent extraction column 45 of the process. It is to be noted that in thus functioning in such dual capacitywithin the system-prior to its passage intothe reaction zone, the hydrocarbon feed to the system enables the realization of the advantages inherent in its use as the absorbent in the carbonylic'product absorber of the process without incurring the introduction of a contaminated" hydrocarbon charge into the reaction zone.

valved. line 64, provides communication between lines It) and 53, and valved. line 66, provides communication between lines It and 31. An aqueous extract phasecomprising the saturated carbonyli'c compounds introduced into column 45, including, for example, acetone, isobutyraldehyde, propiona'ldehyde, acetaldehyde, etc., andwater, is formed within extraction column 45 and eliminatedzther'efrom through valved line 68;

The. aqueous phase'separated in separators 25 and 35 is eliminated therefrom through valved lines lfl'and II, respectively. The aqueous phase thus drawn from separators 25 and 35 will generally comprise only minor amounts of .methacrolein and may beeliminated from the system through valved lines 12 and I3. Residual amounts of carbonylic constituents, including any methacrolein, contained in the aqueous phase separated in separators 25 and 35 maybe removed therefrom, however, by any suitable means, such as, for example, by distillation in a still I4; Carbonylic constituents comprising methacroleinare taken overhead from still I5, and passed through line 15 into line 39; Aqueous bottoms are removed from still I4 by means of valved line (6.

Substantially all carbonylic reaction products are recovered therefore from the efiluent stream leaving the h drocarbon oxidation zone of the process'without the need for any solvent for the absorption o eration other than the hydrocarbon feed to the process,

Q erhead from the absorber 3? will comprise amixture of inert ases saturated with normally gaseous h drocarbons com rising isohutvlene. Residual amounts of isobut lene remaining in the gaseous overhead from absor er 3' are readilv separated econ micall therefrom because of the re uction in volume over the amount of gases normall encountered. in o eration wherein substantiallv all ofthe h drocarbons are com rised in the a sorber overhead. The aseous stream passin throu h line 8" may the efo e he passed tnsu t le means for the recovery of isobutylene th r m.

Suitable mpansfbl. the recovery of r dual isobut lene from the e h ad of column if! may c mprise a. se nd a orpti n one c mp s n a s rpti n c lumn 8 whe e n the aseous stre m is c nt t d r-nunte curr ntl ith a escendin a s r ent stream. such as a hi her boilin hy r c r on stream. for exam le. a as oil. intr duced into the u er part f c lumn Bi by m ns of a ed nev '2. In c umn 8I isobutvlene is absor ed by the as oil stream and inert tail gas, com risin ovides of carbon. nitro en. etc. is elim nated fr m the system throu h val ed li e 83. Gas. oil. enriched with absorbcdis hutvlcne. is passed throu h line 84 to a suitable st ll 85 wherein isohlltvlene is flashed oif. Tsohut ene may be passed throu h valved line 9'1 into li e Ill. In a preferred method of carr ing out the invention. even the isobut lene flowing throu h line 90 is passed. at least in part, into line 53 to be used as part of the secondar orga ic solvent in column Alihefore passin to the oxidation zone. In this wise substantiall all contaminant saturated carbonvlic compounds are removed from all hydrocarbons passed to the oxidation zone. Lean scrubbing medium is returned from the lower part of stripper 85, through lines 86 and 82, to the upper par of absorber column BI. 7

It is to be understood that modifications within the scope of the invention may be made in the process as set forth in the foregoing detailed illustrative description thereof. Thus, modifications may be made in the method employed in cooling the stream passing from reactor I5 to absorber 30, and in the removal of water there-5 from. In a modification of the process of the invention, as illustrated by Fig. II of the attached drawing, the efiluent stream leaving reactor I5 through line 23 is cooled in suitable cooling means, such as, for example, a cooler 2Q, and thereafter compressed to a high pressure- Thus, the cooled stream leaving cooler 24 is passed into compressor 96 wherein. it is compressed, and thence through line 91 into a phase separator chamber 169. Additional cooling means, such as, for example, a cooler 98, are provided to cool the compressed stream flowing through line 91. Further cooling means may be resorted to, for example, the introduction. of a. quenching medium, such as, water, into line 9'! from an outside source by means of valved line 98. In passing through compressor 96 the cooled reactor effluence is compressed to a pressure sufficiently high to enable the formation of three phases, two liquid phases and a vapor phase, within separator 08. The lower liquid phase will consist essentially of water containing formaldehyde and any higher polymeric reaction products formed in the system. The intermediate liquid layer will consist essentially of isobutylene and methacrolein-containing carbonylic reaction products. The vapor phase will comprise methacroleincontaining carbonylic reaction products, hydrocarbons, and normally gaseous components of the reactor affluence. The lower aqueous phase is passed from separator Inf! throu h line H33 into still 54' wherein carbonylic constituents are distilled therefrom as described above. The intermediate liouid phase, consisting of isobutylene 1 and methacroleincontaining carbonylic reaction products is passed through line I02 into line 39. The vapor phase is passed from separator I 90 through line MI into absorber 3!) to be treated therein as described above; The modification of the process wherein the reactor effiuence is compressed to a high pressure reduces substantially the loa placed upon absorber 30 A method of cooling the reactor eiiluence particularly preferred in the production of acrolein by the oxidation of propylene is illustrated by the Fi III of the attached drawing. Therein the efiiuence emanating rom reactor I5 through line 23 is passed through line H35 into a suitable quench ng chamber such as, for example, a tower Hi1. Bafiles, bubble trays, inert packing, or the like may be provided in tower Iil'I. Suitable heat exchanging means such as, for example, an indirect heat exchanger I86, may be provided in line I 05 to enable the withdrawal of heat from the stream flowing through line 23 by indirect heat exchange with a suitable cooling agent which may comprise a side-stream taken from within the system. Within tower I01 the reactor efiluence is passed upwardly countercurrent to a stream of water introduced into the upper part of tower I01 by means of line I58. Heating means such as, for example, a reboiler or a closed heating coil I59, is provided in the lower part of tower I01. Conditions within tower It! are controlled to effect the separation therein of aqueous 13 liquid bottoms containing substantially all formaldehyde and higher boiling polymeric materials formed in the system, but containing no substantial'amount of acrolein. Liquid bottoms are withdrawn from tower I01 and continuously recirculated to the upper part of tower I91 by means of line 108 provided with pump Il-l. Means for controlling the temperature of the water introduced into the upper part of tower I01, such as a cooler, or a heat exchanger H2, is provided in line I98. Conditions within tower I81 enabling the separation of substantially all water of reaction as bottoms, with the passage of substantially all of the desired unsaturated aldehyde overhead, is obtained by control of the temperature of the bottoms in the tower and the water introduced into the top thereof bymeans of coil I99 and exchanger H2, respectively. An amount of water generally at least equal to the amount of water introduced into, or formed within, the reaction zone is bled intermittently or continuously from the system through valved line I 13. A valved line H4 is provided for the introduction of water into line 198. In cooling the reactor efliuence, and separating water therefrom, by the method substantially as illustrated by the Fig. III of the drawing, not more than exceedingly small amounts of the desired unsaturated aldehyde, such as acrolein, will be contained in the aqueous stream eliminated from the system through valved line I I3. The aqueous stream drawn from tower I01 through valved line H3 may be subjected to conventional processing means not shown in the drawing comprising, for example, one or more such steps as distillation, extractive distillation, absorption, and the like, to recover therefrom any carbonylic compounds which may be contained therein. Overhead from tower I01, consisting of effluence from reactor l5 now free of any substantial amount of water, is passed through line H5 into absorber 30, to be treated therein as described in the present detailed description of the invention.

For the purpose of clarity, all parts of apparatus not essential to a complete description of the invention such as, for example, pumps, condensers, accumulators, etc., have been omitted from the drawing and the description of the invention.

EXAMPLE II In two separate operations, A and B, methacrolein of high purity is produced by the direct oxidation of isobutylene in accordance with the invention. The results obtained in each of the separate operations are given throughout the example under separate columns A and B, respectively.

Isobutylene is oxidized to methacrolein by contacting a mixture of isobutylene and air, containing a ratio of isobutylene to oxygen of 5, with a cuprous oxide catalyst in the presence of added steam at a temperature of about 360 for each 100 moles of reactor eflluence. The remainder of the reactor efiluence consists predominantly of normally gaseous materials such 14 as nitrogen, carbon monoxide, carbon dioxide, oxygen. The total carbonylic compounds in the mixture has the following approximate com-- position-in mole percent."

Methacrolein 89. 2 89. 2 Propionaldehyde l. 68 -1. 68 Acetaldehyde 3. 43 3. 43 Acetone 3. 97 3. 97 Acrolein 1. 68 1. 68

The total reactor eiiiuence is compressed, cooled, and introduced into a phase separator resulting in the formation of two distinct liquid phases and a gas phase in the phase separator. The temperature and pressure, and the distribution of the methacrolein and isobutylene (based on 100 moles of reactor eilluence) in the phase,

The gas phase is passed from the phase separator into an absorber column wherein it is brought into countercurrent contact with a stream of liquefied isobutylene which is introduced into the upper part of the absorber from an outside source. The temperature and pressure in th absorber, and the amount of isobutylene introduced as solvent for each mole of methacrolein introduced into the absorber to obtain the absorption of about 99.0% of the methacrolein in the isobutylene solvent are as follows:

Absorber A 13 Temperature, "C 20 30 Pressure, lbs. sq. in. abs 114. 7 114. 7 Isobutylenesolvent required, mol

methacrolein in absorber feed 21. 6 l4. 9 Methacrolein absorption 98. 9 99. 6

Liquid isobutylene containin the absorbed methacrolein containing carbonylic reaction products is taken from the absorber and distilled at 28 lbs. sq. in. abs. to strip isobutylene there. from. Results obtained are as follows:

Absorbate Stripping A B Overhead Composition:

isobutylene, mole percent 99. 9 99. 9

Acetaldehyde, mole percent.-. 1 .09 Bottoms-Composition:

Methacrolein, mole percent; 96. 2 97.1

Propionaldehyde mole percent l. 1 l. 3

Acetone 1.1 8

Acrolein 1. 6 8

The crude methacrolein-containing carbonylic products remaining after stripping the absorbate are combined with the isobutylene liquid phase from the phase separator and the mixture subjected to a, liquid phase extraction in a 20 plate extraction column using water as the solvent in the presence of a secondary organic solvent. The

7 acetaldehyde-contaminated isobutylene stripped consisting essentially of water and saturated carbonylic compounds including isobutyraldehyde, acetaldehyde, acetone, propionaldehyde, etc., is taken from the lower part of the column.

Liquefied propylene, taken from an outside source, is introduced into the top of the absorber column at a controlled rate to obtain absorption of 99.9+% of the acrolein content of th reaction mixture charged to the absorber column. The absorption is carried out at a temperature of C. and at a pressure of 260 pounds per square inch absolute. The operation is repeated under substantially identical conditions with the ex-. ception that water is substituted for the liquefied propylene stream introduced into the absorption column. The amount of solvent required .in each operation to obtain the desired degree of separation is indicated in the following table:

Conditions and results of the liquid extraction are as follows:

Isobutyleneis stripped from the ra-flinate containing less than 0.25 mole percent saturated carbonylic compounds leaving as residue methaorolein of 99.5% purity.

The isobutylene stripped from the raffinate phase of the liquid extraction step is used as charge to the oxidation reactor.

EXAMPLE III Propylene is oxidized by contactin a mixture of propylene and air containing a mole ratio of propylene to oxygen of 6 with a cuprous oxide catalyst at a temperature of about 375 C. in a reactor. The reactor efiluence is introduced into a quench tower wherein it passes upward couna tercurrent to a stream of water introduced into the upper part of the quench tower. The water introduced into the upper part of the tower is maintained at a temperature of from 20 to 50 C. The bottoms of the quench tower are maintained at a temperature of 80 C. to 100 C. Liquid aqueous bottoms containing formaldehyde are withdrawn from the lower part of the quench tower. The cooled effluence now free of any substantial amount of water, is passed overhead from the quench tower into an absorber column having a capacity equivalent to ten theoretical plates. The reactor eiliuence introduced into the absorber column contained 29.3 moles of normally gaseous material consisting predominantly of propylene, carbon monoxide, carbon dioxide, nitrogen, and oxygen, for each mole of total carbonylic compounds. The total carbonylic compounds in the mixture had the following composition:

Percent by weight Acrolein 90.0

Acetaldehyde 6.0 Propionaldehyde 2.0 Acetone 2.0

The absorbate consisting of the acrolein-containing carbonylic reaction products absorbed in propylene in the foregoing Example III is introduced into a distillation column and propylene stripped therefrom. The acrolein-c-ontaining carbonylic residue is subjected to liquid phase extraction using water as solvent in the presence of a secondary solvent. The propylene stripped from the carbonyiic compounds-containing absorbate is liquefied and is used as secondary organic solvent in the liquid phase extraction. A raiiinate phase consisting essentially of acrolein and propylene is taken from the upper part of the column and an aqueous phase consisting essentially of water and saturated carbonylic compounds including acetone, acetaldehyde, propionaldehyde, etc. is taken from the lower part of the extraction column. Conditions used and results obtained in the extraction of the crude acrolein-containing carbonylic reaction product are as follows:

Liquid phase extraction:

Temperature, "C H 20 Pressure, lbs. sq. in. abs. 150 Water entering as solvent 14.3 Propylene entering as solvent 10.0 Acrolein recovery 98.5 Composition rafiinate per cent by weight:

Propylene Acrolein 10 Propylene is stripped from the rafilnate phase and used as charge to the propylene oxidation reactor. Acrolein of a purity of 96.2% remained after distilling the propylene from the raffinate phase.

The invention claimed is:

1. In a process for the production of methacrolein wherein normally gaseous hydrocarbons comprising isobutylene are subjected to isobutylene oxidizing conditions in a reaction zone with the formation of a reaction mixture comprising methacrolein, acetaldehyde-containing saturated carbonylic compounds, normally gaseous hydrocarbons comprising isobutylene and fixed gases, the steps which comprise contacting at least a part of said reaction mixture with liquefied normally gaseous hydrocarbons comprising isobutylene, thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising isobutylene-containing normally gas- 1'7 eous hydrocarbons, methacrolein and acetaldehyde-containing saturated carbonylic compounds, stripping acetaldehyde-containing normally gaseous hydrocarbons comprising isobutylene from said absorbate, thereby leaving a residue comprising methacrolein-containing carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent comprising isobutylene-containing normally gaseous hydrocarbons-in an extraction zone, introducing said acetaldehyde-containing normally gaseous hydrocarbons stripped from said absorbate into said extraction zone in the liquid state tobe used therein as said organic solvent, thereby forming a rafiinate phase comprising methacrolein and isobutylene-containing normally gaseous hydrocarbons substantially free 'of saturated carbonylic compounds in said extraction zone, stripping isobutylene-containing normally gaseous hydrocarbons from said rafiinate phase, and passing normally gaseoushydrocarbons comprising isobutylene stripped from said rafiinate hase into said reaction zone.

2. In a process for the production of methacrolein wherein normally gaseous hydrocarbons comprising isobutylene are subjected to isobutylene oxidizing conditions in a reaction zone with the formation of a reaction mixture comprising methacrolein-containing saturated carbonylic compounds, normally gaseous hydrocarbons comprising isobutylene and fixed'gases, the steps which comprise contacting at least a part of said reaction mixture with liquefied normally gaseous hydrocarbons comprising isobutylene, thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising isobutylene-containing normally gaseous hydrocarbons, and methacrolein-containing saturated carbonylic compounds, stripping normally gaseous hydrocarbons comprising isobutylene from said absorbate, thereby leaving a residue comprising methacrolein-containing carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent comprising isobutylene-containing normally gaseous hydrocarbons in an extraction zone, introducing said normally gaseous hydrocarbons stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent, thereby forming a rafllnate phase comprising methacrolein and isobutylene-containing normally gaseous hydrocarbons substantially free of saturated carbonylic compounds in said extraction zone, stripping drocarbons comprising isobutylene from said raflinate phase, and passing normally gaseous hydrocarbons comprising isobutylene stripped from said rafiinate phase into said reaction zone.

3. In a process for the production of acrolein wherein normally gaseous hydrocarbons comprising propylene are subjected to propylene oxidizing conditions in a reaction zone with the formation of a reaction mixture comprising acrolein-containing saturated carbonylic compounds, normally gaseous hydrocarbons comprising propylene and fixed gases, the steps which comprise contacting at least a part of said reaction mixture with liquefied normally gaseous hydrocarbons comprising propylene, thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising propylenecontaining normally gaseous hydrocarbons and acrolein-containing saturated carbonylic compounds, stripping normally gaseous hydrocarbons comprising propylene from said absorbate, thereby leaving a residue comprising acrolein-containing carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent comprising propylene-containing normally gaseous hydrocarbons in an extraction zone, introducing said normally gaseous hydrocarbons stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent thereby forming a rafiinate phase comprising acrolein and propylene-containing normally gaseous hydrocarbons substantially free of saturated carbonylic compounds in said extraction zone, stripping normally gaseous hydrocarbons comprising propylene from said raffinate phase and passing normally gaseous hydrocarbons comprising propylene stripped from said rafiinate phase into said reaction zone. i

4. In a process for the production of an alphamethylene aldehyde having three to four carbon atoms to the molecule wherein normally gaseous hydrocarbons comprising an olefin having three to four carbon atoms to the molecule are sub- Jected to olefin oxidizing conditions in a.reaction zone with the formation of a reaction mixture comprising an alpha-methylene aldehyde having three to four carbon atoms to the molecule in admixture with saturated carbonylic compounds, normally gaseous hydrocarbons, and fixed gases, the steps which comprise-contacting at least a part of said reaction mixture with liquefied normally gaseous hydrocarbons comprising an olefin having three to four carbon atoms to the molecule, thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising said liquefied normally hydrocarbons and said alpha-methylene aldehydecontaining saturated carbonylic compounds, stripping said normally gaseous hydrocarbons from said absorbate, thereby leaving a residue comprising alpha-methylene aldehyde-containing carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent in an extraction zone, introducing said normally gaseous hydrocarbons stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent, thereby forming a raffinate phase comprising alpha-methylene aldehyde having three to four carbon atoms to the molecule and normally gaseous hydrocarbons comprisingan olefin having three to four carbon atoms to the molecule substantially free of saturated carbonylic compounds in said extraction zone, stripping said normally gaseous hydrocarbons from said raffinate phase and passing said normally gaseous hydrocarbons stripped from said rafiinate phase into said reaction zone.

5. In a process for the production of an alphamethylene aldehyde having at least three carbon atoms to the molecule wherein hydrocarbons comprising an olefin having at least three carbon atoms to the molecule are subjected to olefin oxidizing conditions in a reaction zone'with the formation of a reaction mixture comprising an alpha-methylene aldehyde having at least three carbon atoms to the molecule in admixture with saturated carbonylic compounds, unconverted hydrocarbons, and fixed gases, the steps which comprise contacting at least a part of said reaction mixture with a, liquid stream of said hydrocarbons to be oxidized comprising an olefin having at least three carbon atoms to the molecule, thereby forming a gaseous phase comprismg said fixed gases and a liquid absorbate comprising said hydrocarbons'to be oxidized in admixture with said alpha-methylene aldehydecontaining saturated carbonylic compounds, stripping said hydrocarbons to be oxidizediroin said absorbate, thereby leaving a residue comprising alpha-methylene carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent in an extraction zone, introducing said hydrocarbons stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent, thereby forming a rafilnate phase comprising alpha-methylene aldehyde having at least three carbon atoms to the molecule and said hydrocarbons to be oxidized comprising an olefin having at least three carbon atoms to the molecule substantially free of saturated carbonylic compounds in said extraction zone, stripping said hydrocarbons to be oxidized from said raflinate phase, and passing said hydrocarbons stripped from said ramnatc phase into said reactionzone.

6. In a process for the production or an unsaturated carbonylic compound of the group consisting of alpha-methylene aldehydes and ketones having three to four carbon atoms to the molecule wherein normally gaseous hydrocarbons comprising an olefin having three to four carbon atoms to the molecule are subjected to olefin oxidizing conditions in a reaction zone with the formation of a reaction mixture comprising an unsaturated carbonylic compound of the group consisting of alpha-methylene aldehydes and ketones having three to four carbon atoms to the molecule in admixture with saturated carbonylic compounds, unconverted normally gaseous olefin, and fixed gases, the steps which comprise contacting at least a part of said reaction mixture with liquefied normally gaseous hydrocarbons comprising an olefin having three to four carbon atoms to the molecule thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising said normally gaseous hy drocarbons and said unsaturated carbonylic compound in admixture with saturated carbonylic compounds, stripping said normally gaseous hydrocarbons from said absorbate, therebyleaving a residue comprising said unsaturated carbonylic compound in admixture was carbonylic compounds, extracting said residue with water fiowing countercurrent to an organic solvent in an extraction zone, introducing said normally gaseous hydrocarbons stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent, thereby r forming a rafilnate phase comprising said unsaturated carbonylic compound having three to four carbon atoms to the molecule and said noraldehyde-containing mally gaseous hydrocarbons comprising an olefin having three to four carbon atoms to the molecule free of saturated carbonylic compounds in said extraction zone, stripping said normally gaseous hydrocarbons from said raffinate phase, and passing said hydrocarbons stripped from said raffinate phase into said reaction zone.

'7. In a process for the production of an alpha,- beta-unsaturated carbonylic compound wherein hydrocarbons comprising an olefin having at least three carbon atoms to the molecule are subjected to olefin oxidizing conditions in a reaction zone with the formation of a reaction mixture com prising an alpha,beta-unsaturated carbonylic compound in admixture with saturated carbonylic compounds, unconverted hydrocarbons, and fixed gases, the steps which comprise contacting at least a part of said reaction mixture with a liquid stream of hydrocarbons to be oxidized comprising an olefin having at least three carbon atoms to the molecule, thereby forming a gaseous phase comprising said fixed gases and a liquid absorbate comprising said hydrocarbons to be oxidized and said alpha,beta-unsaturated carbonylic compound in admixture with saturated carbonylic compounds, stripping said hydrocarbons from said absorbate, thereby leaving a residue comprising said alpha,betaunsaturated carbonylic compound in admixture with saturated carbonylic compounds, extracting said residue with water flowing countercurrent to an organic solvent in an extraction zone, introducing said hydrocarbons to be oxidized stripped from said absorbate into said extraction zone in the liquid state to be used therein as said organic solvent, thereby forming a raifinate phase comprising said a1pha,beta-unsaturated oarbonylic compound and said hydrocarbons to be converted comprising an olefin having at least three carbon atoms to the molecule free of saturated carbonylic compounds in said extraction zone stripping said hydrocarbons to be converted from said raffinate phase, and passing said hydrocarbons strippedfrom said raflinate phase into said reaction zone.

ROBERT M. COLE.

CLARENCE L. DUNN.

GINO J. rmao'rrr.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,334,091 Herstein Nov. 9, 1943 2,451,485 Hearne et al. Oct. 19,1948 2,460,056 Yowell et a1 Jan. 25, 1949 

1. IN A PROCESS FOR THE PRODUCTION OF METHACROLEIN WHEREIN NORMALLY GASEOUS HYDROCARBONS COMPRISING ISOBUTYLENE ARE SUBJECTED TO ISOBUTYLENE OXIDIZING CONDITIONS IN A REACTION ZONE WITH THE FORMATION OF A REACTION MIXTURE COMPRISING METHACROLEIN, ACETALDEHYDE-CONTAINING SATURATED CARBONYLIC COMPOUNDS, NORMALLY GASEOUS HYDROCARBONS COMPRISING ISOBUTLENE AND FIXED GASES, THE STEPS WHICH COMPRISE CONTACTING AT LEAST A PART OF SAID REACTION MIXTURES WITH LIQUEFIED NORMALLY GASEOUS HYDROCARBONS COMPRISING ISOBUTYLENE, THEREBY FROMING A GASEOUS PHASE COMPRISING SAID FIXED GASES AND A LIQUID ABSORBATE COMPRISING ISOBUTYLENE-CONTANING NORMALLY GASEOUS HYDROCARBONS, METHACROLEIN AND ACETALDEHYDE-CONTAINING SATURATED CARBONYLIC COMPOUNDS, STRIPPING ACETALDEHYDE-CONTAINING NORMALLY GASEOUS HYDROCARBONS COMPRISING ISOBUTYLENE FROM SAID ABSORBATE, THEREBY LEAVING A RESIDUE COMPRISING METHACROLEIN-CONTAINING CARBONYLIC COMPOUNDS, EXTRACTING SAID RESIDUE WITH WATER FLOWING COUNTERCURRENT TO AN ORGANIC SOLVENT COMPRISING ISOBUTYLENE-CONTAINING NORMALLY GASEOUS HYDROCARBONS IN AN EXTRACTION ZONE, INTRODUCING SAID ACETALDEHYDE-CONTAINING NORMALLY GASEOUS HYDROCARBONS STRIPPED FROM SAID ABSORBATE INTO SAID EXTRACTION ZONE IN THE LIQUID STATE TO BE USED EXTRACTION ZONE IN THE LIQUID THEREBY FORMING A RAFFINATE PHASE COMPRISING METHACROLEIN AND ISOBUTYLENE-CONTAINING NORMALLY GASEOUS HYDROCARBONS SUBSTANTIALLY FREE OF SATURATED CARBONYLIC COMPOUNDS IN SAID EXTRACTION ZONE, STRIPPING ISOBUTYLENE-CONTAINING NORMALLY GASEOUS HYDROCARBONS FROM SAID RAFFINATE PHASE, AND PASSING NORMALLY GASEOUS HYDROCARBONS COMPRISING ISOBUTYLENE STRIPPED FROM SAID RAFFINATE PHASE INTO SAID REACTION ZONE. 